/**
*      author: Y_Yao
*      created: 2025-01-25 20:29:03
**/

#include<bits/stdc++.h>

#define int LL
using namespace std;
using LL = long long;
const LL LLINF = 1e18;
const int INF = 0x3f3f3f3f;
const int N = 1e3 + 7;
char a[N][N];
int h,w;

void solve()
{
    cin >> h >> w;
    int cnt = 0;
    int left = INF,right = -INF,top = INF,low = -INF;
    for(int i = 1;i <= h;i++)
    {
        for(int j = 1;j <= w;j++)
        {
            cin >> a[i][j];
            if(a[i][j] == '#')
            {
                cnt++;
                left = min(left,j);
                right = max(right,j);
                top = min(top,i);
                low = max(low,i);
            }
        }
    }

    for(int i = top;i <= low;i++)
    {
        for(int j = left;j <= right;j++)
        {
            if(a[i][j] == '#')
            {
                cnt--;
            }
            if(a[i][j] == '.')
            {
                cout << "No" << endl;
                return;
            }
        }
    }
    if(cnt != 0)
    {
        cout << "No" << endl;
    }
    cout << "Yes" << endl;
}

signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);

    int t = 1;
    //cin >> t;
    while(t--)
    {
        solve();
    }
    return 0;
}